One or two bars of soap. The travel-size bars the hotels give you aren't good for more than one shower.

Full-sized bottles of shampoo and conditioner. The travel-size bottles the hotels give you aren't enough for a single person with a full head of hair.

Washcloths or scrubbies. The ones they give you don't get you clean, but work well as coasters.

Locks for luggage. Don't trust the housecleaning staff to not go through your things (some of my stuff was stolen at Tekkoshocon 2005).

A roll of duct tape. You never know when you'll have to fix something.

Wireless network card and ethernet cable for your laptop. More and more hotels are providing free net.access for guests.

Acts of God aren't always what you want God to do, or what you think God really thinks.

On a Linux machine with a wireless network interface, if you want to get an idea of the wireless networks around you, su over to the root user and execute the command iwlist scan, which uses the iwlist utility from the wireless toolset (standard on many distros these days). This probes the wireless network adaptor driver and tells it to report all of the networks (listed in the output as cells) that it's detected.

On Linux machines you can change the hardware address of the network interfaces for various reasons. Hardware addresses uniquely identify your card (sort of) so that you won't confuse the switches/routers of the network your machine is attached to. I say 'sort of' because the MAC addresses assigned by a particular manufacturer can and do wrap around from time to time, but because the duplicates are (hopefully) in different lots, the probability of two cards on your LAN having the same hardware address is astronomically high. Anyway, if you ever need to change the hardware address the card's driver thinks it has, log into the box as root and make sure the card is active (ifconfig ethX up if it isn't). Execute the following command: ifconfig ethX hw ether AA:BB:CC:DD:EE:FF, where AA:BB:CC:DD:EE:FF is an arbitrary set of pairs of hexadecimal digits (for example, 03:74:D2:12:9B:C0). Please note that not all drivers support this, but many do these days.

Never underestimate the lengths that asshats will go to in an effort to make life interesting.

Never underestimate the power of weird stuff happening.

Rule #1 of being a badass: Never let 'em see you sweat. Ever. You've seen it all and lived to not care enough to tell the tale. Facing down guns, rifles, and rampaging fratboys is all in a day's work for you. You've overthrown peaceful democracies before lunch and dined with dictators in the penthouse the very same night. Lone heroes with nothing to lose don't faze you. You eat phosphorous and just happen to have tracer rounds hidden in your hair seconds later.

Being a badass is half attitude and half careful planning. Even if you're girly-screaming with panic inside your head, you're cool as liquid nitrogen.

Sysadmins are busy people, so whenever they schedule vacation time they really need it, and would very much like to not be contacted while they are on vacation. Unfortunately, many computers and computerised office appliances are like unruly children when the teacher leaves the room to go to the bathroom: They start acting up, acting strangely, and wreaking havoc the moment they are unsupervised.

Whenever you have a suitcase sitting on the floor to pack, you will stub your toes on it at least twice.